This application claims the priority of German patent document 100 1 813.0, filed Jan. 18, 2000, the disclosure of which is expressly incorporated by reference herein.
The invention relates to a method and apparatus for determining air flow and pressure data of a manned or unmanned aircraft or an aerodynamic vehicle.
Conventional air data systems preferably determine the present and local flow angles of an aircraft as well as the present and local static and dynamic pressures, or only some of these values. From these local values so-called undisturbed values are determined in the normal way, i.e. angle of incidence, angle of yaw as well as pressures which are present at the time in the flow which is undisturbed by the aircraft. These undisturbed values serve to determine the attitude and the speed as well as further flight-specific values of the aircraft.
Usually, such conventional air data systems are based on the measurement of pressures, for which pitot pressure sensors, which protrude from the aircraft contour, are used. Furthermore there are measuring devices which measure the pressure distribution at the surface of the nose of the fuselage. Alternative or additional options include the use of angle of incidence transmitters and angle of yaw transmitters of the wind-vane type which also protrude from the aircraft contour. In order to measure flow conditions on the aircraft, it is also possible to use optical laser measuring methods. However, due to their size and complexity, and due also to uncertainty in frequency and extent of the aerosols in the air, such optical laser methods are not suitable for operational use as yet.
The measuring sensors protruding from the aircraft contour are associated with the disadvantage in that they increase the overall resistance of the aircraft. Furthermore, they are also endangered by possible impact from foreign objects, such as birds. There is a further disadvantage in that many aircraft comprise an active onboard radar in the front part of the fuselage nose-section, so that no such measuring sensors can be provided in this region without disturbing the function of the onboard radar. However, placing the measuring sensors in the region behind the front fuselage nose-section requires very considerable calibration and correction effort for operational use.
Measuring the pressure distribution at the front point of the fuselage or at other parts of the aircraft facing the airflow, can also be carried out by pressure sensors integrated in the surface. This technique provides the advantage that it does not increase the overall resistance of the aircraft. Also military detectability of the aircraft as a result of measuring sensors protruding from the aircraft contour is not significantly worsened, due to the small radar signature. This type of measuring sensor, however, does pose the danger that measurements may effectively be changed as a result of, for example, ice formation, dirt or bird strike. Consequently, pressure measurements are considerably affected or even impossible, which may lead to total failure of at least individual sensors and even of the air data system.
It is thus the object of the invention to create a relatively uncomplicated method and apparatus for measuring air data for an aircraft.
Another object of the invention is to provide such a method and apparatus which is substantially resistant to the influence of objects or conditions in the environment of the aircraft.
These and other objects and advantages are achieved by the method and apparatus according to the invention, which includes no components protruding from the fuselage surface of the aircraft, requires no pressure boreholes for measuring the pressure at the surface; and is resistant to the effect of objects or foreign objects as well as to unfavorable environmental conditions. In the measurement system according to the invention, a measuring device is used to measure forces that occur between front and rear fuselage sections of the aircraft. The information is then used to determine the desired air data by comparison with at least one calibration curve. An acceleration sensor is also provided to measure inertial forces which bear on the front fuselage section, for example as a result of aircraft maneuvers.
By integrating the measuring system into the front fuselage region (e.g., in the sectional plane between radome and aircraft fuselage), interference with the onboard radar accommodated in the nose of the fuselage or in the front fuselage section is avoided. Furthermore, with the arrangement of the measuring device according to the invention in the region behind the front fuselage section containing the onboard radar, measuring accuracy is not jeopardized so that system expenditures for measured data correction are increased.
Other objects, advantages and novel features of the present invention will become apparent from the following detailed description of the invention when considered in conjunction with the accompanying drawings.